The present invention is related to cutting instruments, and more specifically folding knives with locking mechanisms to prevent the inadvertent closure of a knife blade associated with the folding knife.
Cutting instruments have been used for centuries by craftsmen, hunters, and others requiring a sharp cutting instrument. More recently, fixed length knives have been replaced with popular folding knives which generally have two positions. In a first extended position of use, the folding knife cutting blade is extended to expose the blade cutting edge and permit cutting therein. In a second closed position, the cutting edge of the blade is stored within a cavity in the handle portion of the knife, thus preventing the blade from being exposed and providing a cutting instrument which is much shorter in length than a typical fixed blade knife. Although these types of knives are extremely convenient, they can potentially become dangerous if the cutting blade does not have a locking mechanism to securely keep the knife blade in the first extended position of use. Likewise, it is often convenient to have a locking mechanism or some form of frictional ball detente apparatus to prevent the knife from inadvertently opening when the knife blade is in the second closed position.
Numerous attempts have been made to provide locking mechanisms which prevent a knife blade from inadvertently opening, closing, or both. One of the most commonly known locking mechanisms is a xe2x80x9cback lock.xe2x80x9d The back lock uses a longitudinal length of rigid material, most commonly stainless steel, which pivots about a pivot point near the forward portion of the back lock. By applying pressure to a rearward portion of the locking mechanism, the locking mechanism rotates about the pivot point and releases a tang engagement mechanism from the heel portion of the knife blade. As the heel portion is released, the knife blade is released from the locking mechanism and is allowed to rotate from the first extended position to the second closed position. Although convenient to use, the back lock is not particularly strong and has a tendency to fail when excessive pressure is applied to the upper edge of the knife blade.
Another type of locking mechanism commonly used for folding knives is generally referred to as a xe2x80x9cliner lockxe2x80x9d. A liner lock generally comprises a metallic leaf spring which is biased and positioned within the cavity of a knife handle and interconnected to one of the scales which comprises the knife handle. Upon opening of the knife blade to a first extended position of use, the forward or tang end of the leaf spring extends outwardly from the scale and behind the heel portion of the knife blade, thus preventing the knife blade from being closed without pushing the leaf spring liner lock to the side of the heel end of the knife blade, thus allowing rotation of the knife blade to the second closed position. Although simplistic in design, liner locks can potentially fail if excessive force is applied to the upper edge of the knife blade. During failure, the liner lock has a tendency to bow or otherwise deform, due to the extended length of the liner lock and the thin nature of the material required to fit within the knife handle cavity.
Although there are other types of locking mechanisms used to prevent the inadvertent closure of a folding knife blade, none are simplistic to use, inexpensive to manufacture and are essentially fail-proof. Thus, there is a need for a type of folding knife locking mechanism which is simplistic to use, inexpensive to manufacture, and provides substantial strength to prevent any inadvertent failure.
It is thus an object of the present invention to provide a folding knife locking mechanism which is substantially non-defeatable when pressure is applied to the back edge of the knife blade when the blade is in an extended position of use. It is a further object of the present invention that the folding knife locking mechanism be designed to use a minimum number of components, thus making the locking mechanism inexpensive to manufacture, simplistic in design, and encompassing a variety of different embodiments for use with a number of different folding knife designs.
It is a further object of the present invention to provide a locking mechanism which utilizes a compressive force generated over a very short distance between the blade stop pin and the heel end of the blade. This geometric configuration substantially prevents the locking mechanism from failing during use.
Thus, in one aspect of the present invention, a locking mechanism is provided which positions a tang between the stop pin of the knife handle and anvil portion of the heel end of the knife blade. When a force is applied to the upper edge of the knife blade, the tang of the knife locking mechanism is compressed between the anvil end of the heel end of the knife blade and the stop pin. This unique positioning of the tang allows the locking mechanism to withstand substantial forces.
Thus, in one particular aspect or embodiment of the present invention, a folding knife with a compression locking mechanism is provided which generally comprises:
a handle having a front end, a rear end and a cavity defined therebetween;
a knife blade having a front end, a heel end with an anvil, a cutting edge and an upper edge, said heel end rotatably interconnected to said front end of said handle wherein said knife blade travels between a first extended position of use and a second closed position with said knife blade cutting edge positioned within said handle cavity;
a stop pin positioned within an upper edge of said handle cavity for engaging an upper portion of said heel end of said blade when said knife blade is in said first extended position of use;
a locking mechanism positioned proximate to said handle cavity, said locking mechanism comprising a tang releasably positioned between said anvil of said blade and said stop pin when said knife blade is in said first extended position of use, wherein when pressure is applied downward on said upper edge of said knife blade, said tang is compressed between said blade anvil and said stop pin to prevent inadvertent closure of said knife blade.